Social media managers spend a lot of time resizing images for different platforms. This can be a tedious task that involves cropping and adjusting dimensions. 
http://www.croptor.com is a tool that can help you batch process images. You simply upload your images, select the desired output sizes for different platforms, and Croptor.com will resize the images for you. 
This can save you a lot of time and frustration, especially if you manage social media for multiple brands or clients. The free plan has limitations, but the paid option is affordable and well worth the investment. 
I highly recommend giving http://www.croptor.com a try. It could become an essential part of your social media workflow. 
 
Have a good Day